procfs: fix some wrong error code usage

[root@wei 1]# cat /proc/1/mem
cat: /proc/1/mem: No such process

error code -ESRCH is wrong in this situation. Return -EPERM instead.

Signed-off-by: Jovi Zhang <[e-mail]>
Reviewed-by: KOSAKI Motohiro <[e-mail]>
Cc: Alexey Dobriyan <[e-mail]>
Cc: Al Viro <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

fs/proc/base.c

···
 	if (!task)
 		goto out_no_task;
 
-	if (check_mem_permission(task))
+	ret = check_mem_permission(task);
+	if (ret)
 		goto out;
 
 	ret = -ENOMEM;
···
 	if (!task)
 		goto out_no_task;
 
-	if (check_mem_permission(task))
+	copied = check_mem_permission(task);
+	if (copied)
 		goto out;
 
 	copied = -ENOMEM;
···
 	if (!task)
 		goto out_no_task;
 
+	ret = -EPERM;
 	if (!ptrace_may_access(task, PTRACE_MODE_READ))
 		goto out;